Memory cards are used as storage devices for various electronic appliances such as a PDA, a digital camera or a camcorder.
FIG. 1 is a view showing one surface of a memory card according to the related art.
Referring to FIG. 1, in the memory card 10, a semiconductor device comprising a memory device is mounted on a printed circuit board for the memory card and the mounted semiconductor device is sealed with a resin molding part. In addition, a terminal part 11 is formed on, one surface of the memory card to sever as a connector for electrically connecting the memory card to an electronic appliance employing the memory card.
Meanwhile, since the terminal part 11 has the connector function with respect to the external electronic appliance, the product yield of the memory card 10 may be lowered if a defect, such as a scratch or an imprint, if formed on the terminal part 11.
FIGS. 2a to 2h are sectional views showing a process of fabricating a printed circuit board for a memory card according to the related art.
Referring to FIG. 2a, the printed circuit board for a memory card comprises a terminal part 31 formed on a bottom surface of an insulating layer 30 and a mounting part 32 on a top surface of the insulating layer 30. Although not shown, the terminal part 31 and the mounting part 32 may be electrically connected to each other through a via hole in which a conductive material is filled, so that a circuit may be formed.
The terminal part 31 provides a connector function of electrically connecting the mounting part 32 formed on the top surface of the insulating layer 30 to an external electronic appliance. The mounting part 32 forms a circuit or allows a resistor or a capacitor to be mounted thereon. In addition, the mounting part 32 provides a function of a metallic pad for electric connection with a memory device.
A PSR (Photo-imageable Solder Resist) 33 is formed on the top and bottom surfaces of the insulating layer 30 to expose portions of the terminal part 31 and the mounting part 32.
Referring to FIG. 2b, a first photosensitive dry film 34 is formed on and under the insulating layer 30, and the mounting part 32 for providing the function of the metallic pad is exposed through an exposure and development process.
Referring to FIG. 2c, a soft gold layer 35 is plated on the mounting part 32 for providing the function of the metallic pad. The gold soft layer 35 can be subject to the gold wire bonding and may have a merit in soldering.
As shown in FIG. 2d, the first photosensitive dry film 34 is removed.
Referring to FIG. 2e, a second photosensitive dry film 36 is formed on and under the insulating layer 30 and the terminal part 31 which provides the connector function is exposed through an exposure and development process.
Referring to FIG. 2f, a hard gold layer 37 is plated on the terminal part 31 having the connector function.
Since the hard gold layer 37 has a high surface strength and high resistance against corrosion, the hard gold layer 37 is plated on a portion frequently coupled/decoupled with an electronic appliance, such as a connector of a memory card electronic appliance.
Referring to FIG. 2g, the second photosensitive dry film 36 is removed. Before the second photosensitive dry film 36 is removed, in order to prevent the hard gold layer 37 from being damaged, a protective layer (not shown) may be additionally formed.
When the process described above is performed, the printed circuit board for a memory card may be fabricated. After the printed circuit board is fabricated, a memory semiconductor chip and a memory controller are attached to the printed circuit board to form the memory card.
That is, as shown in FIG. 2h, a memory device 40 is mounted on the photo-imageable solder resist 33 formed over the insulating layer 30 and the memory device 40 is electrically connected to the soft gold layer 35 through a wire 39. For example, the memory device 40 may include a memory chip and a memory controller.
In addition, a molding member 41 is formed to the top side of the insulating layer 30 comprising the memory device 40 and the soft gold layer 35. The molding member 41 is formed by using an epoxy molding material called EMC (Epoxy Molding Compound), so that the molding member 41 protects circuit components comprising the memory device 40 from an external shock or environment.